‘Tis the season for the obligatory “best of” lists for 2013. We thought we’d take a look back at some of this year’s notable outbreaks. Our list is randomly ordered and by no means exhaustive- in fact, we’ve limited it to the nice round number of ten. We would love to hear your feedback! What outbreaks had significant impacts on you and your community this year?

Middle East Respiratory Syndrome coronavirus, or MERS-CoV

While MERS was first detected in 2012, the bulk of the cases reported thus far have occurred in 2013. From September 2012 to date, 165 laboratory-confirmed cases and 71 deaths due to MERS-CoV have been reported to the World health Organization. Cases have been identified in Jordan, Saudi Arabia, the United Arab Emirates, Qatar, Oman, Kuwait, France, Germany, the United Kingdom, Italy, Spain and Tunisia. Much remains to be discovered about this virus, namely, how it infects humans, but we have learned a few things over the past year. In early November, PLoS published a paper by the WHO MERS-CoV Research Group that comprehensively examined what is known about the virus thus far.

Most MERS patients, thus far, have had at least one underlying condition and have experienced severe respiratory disease (severe enough to require being in the intensive care unit). There have been about 51 ‘sporadic’ cases, meaning that they reported no known contact with other MERS cases and they occurred in areas with no known cases in the previous two months.

Symptoms of MERS include fever, cough, chills, pneumonia and the need for respiratory support. There is no specific treatment yet, but patients have been treated with organ support and antivirals and antifungals to prevent other opportunistic infections.

The WHO MERS-CoV Research Group cites a few other studies that have looked at the pandemic potential of MERS. Evidence suggests that, despite frequent comparisons to SARS, MERS does not have the same power as SARS. In fact, studies suggest that the virus does not yet have pandemic potential. The virus is likely, however, to continue to spread due to human-to-human transmission. Scientists believe that there is likely an epidemic occurring among animals and what we are seeing is a spillover into humans. We do not know what the animal reservoir is, but genetically similar coronaviruses have been found in hedgehogs and bats.

Polio remains endemic in three countries: Afghanistan, Nigeria and Pakistan. There are a handful of other countries, dubbed “importation countries” by the Global Polio Eradication Initiative, that are susceptible to imported polio due to low immunization rates, travel and instability. Among those countries are: Democratic Republic of the Congo, Niger, Somalia, and the Syrian Arab Republic. In 2013, wild poliovirus has been detected and reported to the World Health Organization in environmental samples in Egypt, Israel, Gaza and the West Bank, and in people in Kenya, Somalia, Cameroon, and Syria. Due to the instability in Syria, and the frequency and scale of population movement, the WHO considers the risk of polio-transmission to be high and is recommending that all travelers to and from the area be vaccinated against polio.

In case you were beginning to feel too negative due to outbreak news, we thought we’d toss in something wonderful: this year, Colombia became the first nation to eliminate river blindness.

River blindness is a parasitic disease, caused by Onchocerca volvulus worm. The parasite is transmitted to humans through the bite of infected black flies. Once inside, the parasites mature, mate, and release offspring. When the worms die in the body, they cause conditions such as rashes, skin lesions and blindness.

On July 29 2013, the WHO verified that Colombia had eliminated onchocerciasis and is the first country in the world to do so. According to a press release from the Pan American Health Organization (PAHO), Colombia has maintained a concentrated control/ elimination (?) effort for sixteen years. The country has engaged communities, rolled out education campaigns, increased and strengthened surveillance efforts, and improved basic sanitation.

Cyclospora is a foodborne parasite (Cyclospora cayetanensis) that is endemic in many tropical and subtropical regions. The parasite infects the small intestine and causes symptoms like watery and frequent diarrhea, lack of appetite, weight loss, fatigue and stomach pains. Symptoms can last from a few days to a few weeks. Treatment includes a combination of antimicrobials and fluid intake.

The CDC’s final tally for this outbreak is 631 cases of cyclosporiasis from 25 states. The outbreak started in mid-June and was declared “over” by the U.S. Food and Drug Administration in late November. According to the FDA investigation, the culprit was bagged salad from Taylor Farms in Mexico. The salad had been served at certain Red Lobster and Olive Garden restaurants in Iowa and Nebraska.

Until this year, Mexico had been free from cholera since its 1991 – 2001 epidemic. From September until November and according to the most recent update from the World Health Organization, Mexico reported 180 cholera cases and one death. Research showed that the source of contamination was the Hidalgo River, and the strain of cholera was very similar to the strain circulating in Cuba, the Dominican Republic and Haiti.

Cholera is caused by the bacterium vibrio cholerae and triggers diarrhea and dehydration. It is spread through the ingestion of contaminated food and water. To prevent cholera infection when traveling in areas where cholera is a risk, the CDC recommends drinking boiled or treated water, washing your hands before eating and after using the restroom, and avoiding raw vegetables.

In March 2013, Princeton University reported its first case of meningococcal disease. Meningitis refers to the inflammation of the membranes around the brain and spinal cord. This condition can be caused by several microbes - one of them, a bacterium called Neisseria meningitides. This bacterium causes meningococcal disease, which in turn can result in meningitis (brain and spinal cord membrane swelling). There are six different serotypes of meningococcal bacteria: A, B, C, X, Y and W-135. There are vaccines for A, C, Y, and W-135, but no vaccine against the B serotype is currently approved for use in the United States.

Since March, eight cases of meningitis B have been reported from Princeton University and four cases have been reported from University of California at Santa Barbara. On December 9, after receiving permission from the FDA and the CDC, a meningitis B vaccine called Bexsero, that has been approved for use in Europe and Australia, was made available in Princeton.

Ah, the bird flu. On April 1 2013, news broke of H7N9 infecting humans in China for the first time. Prior to this year, H7N9 had been known to only infect birds. The first cases were identified in Shanghai and Anhui Province. There have been 147 cases and 47 deaths since April. The outbreak has affected 14 different Chinese provinces.

Health officials do not yet know how humans are becoming infected with the H7N9, but they suspect the source of infection is animals after the virus had been found in chickens, pigeons, and ducks.

Symptoms of infection include fever, shortness of breath and pneumonia. There is no vaccine for H7N9 as of yet. The WHO has not issued any travel warnings in relation to this outbreak, but has recommended that people practice good hand hygiene (washing hands before, during and after food preparation, after using the restroom, after visiting or caring for someone who is sick, and after handling animals) and respiratory hygiene (cough or sneeze into your elbow).

Measles was eliminated from the United States in 2000, however, cases are continuously imported from other countries. Since 2000, the years with the highest recorded number of measles cases were 2008 (140 cases) and 2011 (220 cases). Between January and August of 2013, the CDC reports 159 measles cases within the United States. According to the CDC, the majority of these cases came from three outbreaks, which were in communities with people who abstained from vaccination due to religious or philosophical beliefs. The CDC cautions that an increase in declinations of vaccinations could “threaten the elimination of measles within the United States.”

Seasonal Influenza

This year began with a little bit of excitement around the flu season as the 2012-2013 season got off to an early start. The CDC calls the 2012-2013 a “moderately severe season,” with one of the highest recorded percentages of outpatient visits for influenza-like illness since 1997. The CDC also reports that the number of influenza-associated hospitalizations for individuals over 65-years-old was one of the highest of the past decade.

Chikungunya is a mosquito-borne disease typically found in countries in Asia and Africa. When it was recently detected in the Caribbean island of St. Martin, I would wager the general sentiment was disappointment but not surprise. You may recall that other mosquito-borne diseases, such as West Nile and dengue, have been expanding their reach over the past few years possibly due to travel, climate change, and international business. At the time of this writing, Martinique's first two cases of chikungunya were reported.

Chikungunya is transmitted by the Aedes aeygpti mosquito. Symptoms include fever, chills, muscle aches, and arthritic joint pain. There is no vaccine for chikungunya. The U.S. Centers for Disease Control and Prevention (CDC) recommends using insect repellent, wearing long sleeves and pants, and removing containers that hold stagnant water, to prevent infection.

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